The primary objectives of the proposed research are to isolate and characterize the gonococcal siderophore; to define further its role in pathogenesis of infections caused by N. gonorrhoeae; to determine its role in serum sensitivity or resistance of N. gonorrhoeae, and in resistance and sensitivity to phagocytosis and intracellular killing; and to attempt to identify the outer membrane protein which is responsible for recognition of the siderophore and iron transport in gonococci. The siderophore will be produced and extracted from a diphasic iron-deficient medium, which we have developed, which stimulates (or derepresses) gonococcal siderophore production. Effects of the siderophore on virulence will be evaluated experimentally in the chick embryo model. The availability of iron and the microbial ability to acquire iron may explain a variety of perplexing clinical observations on infections with N. gonorrhoeae.